Cellular network service subscribers typically subscribe to a specific calling plan that permits them to engage in calls up to a certain number of minutes in a specific geographic region over a certain time period. For example, a calling plan for a U.S. cellular network service subscriber may permit the subscriber to engage in calls via the Mobile Network Operator (MNO) network associated with the cellular service for 1000 minutes a month within the continental United States for a flat monthly fee. However, if the subscriber engages in long distance calls outside of the continental United States (e.g., to Canada or to Hawaii), then additional charges will be applied to the subscriber's account. The additional charges will typically be at a much higher per-minute cost than the per-minute cost applied to regular calls within the subscriber's calling plan.